High-tension-current transformer



Feb. 21, 1928. l 1,660,214

F. AHRBERG ET A.

HIGH TENSION CURRENT TRANSFORMER Filed Dec. 9. 1924 Patented Feb. 2l, 1928 PATENT FFEQ BURG, AND KARL SCHRADER,

F .'BERLIN-HALENSEE,I GERMANY, ASSIGNORS TO SIEMENS @t HALSKE, AKTIENGESELLSCHAFT, .OF SIEMENSSTADT, NEAR BERLIN,

GERMANY, A CORPORATION OF GERMA HIGH-TENSION-CURRENT TRANSFORMEB.

Application led December @ur invention relates to improvements in high-tension current transformers.

In the construction of current transformers eorts were hitherto made to employ a 5 minimum number of ampere turns in order to keep the electro-dynamicrepulsion forces within permissible of short-circuits may attain extraordinary high values, so that the current transformer 9 could be considered short-circuit proof. A comparatively large quantity of iron was therefore employed in such transformers because the saturation must be kept low'in spite of the desired capacity in order to l5 avoid no-load currents which would increase the error limits to an inadmissible extent.

@ur invention is based upon the recognition that by the employment of an annular iron core and an annular high-tension wind- 2@ ing which intersect one another at right angles in known manner the electro-dynamic forces act purely centrifugally and the strength of the current transformer against such forces is equally as high as, for instance, in the single conductor current transformer which is also provided with an annular core. Y

According to our invention the number of the ampere turns is chosen so high that the $0 weight of the iron is approximately equal to or less than the weight of the copper of the high-tension winding. By a 'high number of ampere turns a reduction of the transformation as well as of the angle error or a reduction of the cross-sectional area of the iron or a reduction in both is generally attained. ln the present case particular use has been made of the latter characteristic feature. This assumes the employment of a very good insulation of the high-tension winding or primary coil from the iron core and from the low-tension winding or secondary coil. Accordin to my invention this insulation is olotainedg7 by solid insulation materials in such a manner that these materialsQrunning as far as possible along equipotential coil surfaces, subdivide the arcing path of any high voltage discharge to a high e ee.

Ignr the drawing aiixed to this specification and forming part thereof two embodiments of our invention are illustrated by way of example. This drawing represents in limits which in the event- 9, 1924, Serial No. ?54;,785, and in Germany December 1l, 1928.

Fig. 1 a partial elevation and partial section in the plane of the high-tension winding of one construction of the improved transformer,

Fig. 2 a section at right-angles to Fig. l, with the core carrying the low-tension winding in elevation and Fig: 3 a perspective view of another construct1on.

Similar parts are indicated by like characters in all the figures of the drawing.

Referrin to Figures l and 2, it represents the termina leads of a circular loop or coil w having a few windings fed with high-tension current. ln other words these leads may be connected directly into the high tension line. This high tension coil w which forms the primary winding of the transformer, passes thru the window of an iron ring core e at right angles to the core plane7 the window being very much larger than the transverse section of the assembled windings of the coil, so that a comparatively large intervenin space remains between the coil turns and t e iron core. rllhis coil is surrounded by a paper insulation p consisting of wrapped layers of paper, and at the place where the iron core e, carrying the secondary winding 'v surrounds the primary winding at right angles to its plane the wrappin lis of such thickness that it completely fills up the entire intervening space of the window. The paper wrappingthen symmetrically gradually diminishes at both sides towards and up to the point where the supply wires it from the high-tension winding enter and issue, in order that the winding may be sufficiently cooled. In order to prevent a radial leakage from the less insulated portions of the winding to the-iron core a saddle-like screen s is mserted into the remaining open space of the winding which consists of a number of layers of heavy paper or similar insulating material which adapts itself substantially to the e uipotential surface portions of the coil so t at an extremely reat safety against leakage or disruptive discharge of any kind is attained. The insulation p is saturated with oil or ahy other suitable insulating substance `which is liquid when applied but becomes The whole current transsolid later on. former may also be immersed 1n oil. The

. place by attachment of. the current transformer takes means. of angle-iron {ish-plates a olted tothe iron'V core e. The high-tension winding lw is secured in position upon the core e owing to its insulation accurately filling the core window.

The current transformer illustrated in Fig. 3 is exclusively intended for oil insulation and is therefore arranged in an oil tank not illustrated in the drawing. In this construction the direct insulation p1 of the highterision winding fw is of uniform thickness buticomparatively thin and to ll the space a number of insulating protective screens a', l of superimposed layers of paper or the like overlappingone another are provided within the core window or opening. As in the first described construction an insulating screen s of folded paper or thelike is disposed between the outer` circumference of the core e and the high-tension winding w. To prevent arcing between these two screens cufflike insulating bodies m of the same material as the other screens are pushed over the high-tension conductor uz adjacent to the places where the two firstnientioned screens meet. The arrangement and the object'of all theseinsulatingscreens is here such that following as far as possible the equipotential surfaces of the coils they interrupt the insulating layers of oil at several points and thus considerably increase its total disruptive strength.

core, the terminals of said prima What we claim as our invention is 1. In a current transformer for high tens1on currents'in combination a primary high tension coil, a secondary coil, an annular iron core having a window and carr ing said seco ndary coll, said primary coil passing at rlght angles to the plane of said core through the center of the window of said annular core, the terminals of said primar winding lying within the plane but outsi e of said core, and a plurality of thin layers of solid lnsulating material enclosing said primary winding and being arranged substantially at ri ht angles to the ath of disruptive high vo tage discharges, the number of said layers varying in diferent portions of said winding, the maximum number being located at the point where the windin passes through said window and being su cient. in number to lill up substantially the entire intervening space of the window of said core.

2. In a current transformer for high tens1on currents in combination a primary high tension coil, a secondary coil, an annular iron core having a Window and carrying said secondary coil, said primary coil rpassing at right angles to the plane of said core through the center of the window of said annular winding" lying within the lane but' outsi e of said core, and a plurality of thin layers of solid insulating material enclosing said primary winding and said side of winding and being the point where the winding passes through said window and being sufficient in number to fill up substantially 'the entire intervening space of the window of said core, the number of layers gradually decreasing, sym'- metrically on both sides of the iron core plane, towards said coil terminals.

3. In a current transfornlcr for high tension currents in combina-tion an annular shaped primary high tension coil, a secondary coil, an annular iron core having a window and carrying said secondary coil, said primary coil passing at right angles to the plane of said core through the center of said window and insulating means for enclosing said primary winding and being arranged substantially at right angles to the path of disruptive high voltage discharges, and a separate screen of solid insulating material interposed between said primary winding and said secondary coil outside of said window.

4. In a current transformer for high tension currents in combination an annular shaped primary high tension coil, a secondary coil, an annular iron core having a window and carrying said secondary coil, said primary coil passing at right angles'v to the plane of said core through the center of` said window and insulating means for enclosing said primary winding and being arrange substantially at right angles tothe path of disruptive high voltage discharges, and a substantially annular screen of insulating material interposed between said primary secondary coil outside of said window.

5. In a current transformer for high tension currents in combination an annular prl-4 mary hi h tension coil, a secondary coil, an annular iron core having a window and carrying said secondary coil, said annular primary coil passing at right angles to the plane of said core through the center of said window, the terminals of said annular primary coil lying within the plane but outside of said core, and insulating means for totally enclosing said annular primary coil, said insulating means being arranged substantially at right angles to the path of the disruptive high voltage discharges.

6. In a current transformer for high ten'- sion currents in combination an annular primary hi h tension coil, a secondary coil, annular lron core havin rying said sondary coil, said annular priplane of said core through the center of said window, and the terminals of said annular primary lcoil lying within the plane but outsaid core, and insulating means for a window and cariis totally enclosing said annular primary coil, said msulating means being arranged substantially at right angles to the path of the ldisruptive high voltage discharges, said insulatmg m'eans being placed so that its surface follows to a greater part ot its total extension equipotential lines ot' the winding surface of said annular high tension coil.

'i'. In a current transformer for high tension currents in combination an annular primary high tension coil,.,1 secondary coil, an annular iron core havincr a window and carrying said secondary co1l, said annular primary coil passing at right angles to the plane of said core through the center oi' said Window and a plurality of separate layers of solid material for totally enclosing said annular high tension coil, each of said plurality of layers being arranged substantially at right angles to the path of the disruptive high voltage discharges.

8. 1n a current transformer for high tension currents in combination an annular primary high tension coil, an annular iron core having a window and carrying said Secondary coil, and having a cross section as will bring its Weight near to that of said annular primary coil, said annular primary coil passing at right angles to the plane of said core through the center of said Window and insulating means for totally enclosing said primary coil, said insulating means being arranged substantially at right angles to the path of the disruptive high voltage discharges and having a thickness Within the Window of said core so as to substantially ll up the intervening space in said Window.

9. In a current transformer for high tension currents in combination an annular primary high tension coil, a secondary coil, an annular iron core having a Window and carrying said secondary coil, and having a cross section as will bring its weight near to that of said annular primary coil, said annular primary coil passing at right angles to the plane of said core through the center of said window, and a plurality ot' thin layers otl solid insulating material for totally enclosing said annular primary coil, the greater number ot' said layers following eqnlpotential lines of said annular primary coil, said layers substantially lilling up the intervening space in said Window.

l0. In a current transformer for high tension currents in combination an annular primary high tension coil, a secondary coil, an annular' iron core having a window and carrying said secondary coil, said primary coil passing at right angles to the plane of said core through the ccnterof said Window, the terminals of said annular primary coil lying within the plane but outside of said core, and a plurality of thin layers of s olid insulating material for totally enclosing said annular primary coil, the greater number of said layers following equipotential lines of said annular primary coil, and substantially filling up the intervening space in said Window.

In testimony whereof we aflix our signatures.

FRITZ AHRBERG. GEORG KEINATH. KARL SCHRADER. 

